Switches with magnetically coupled armatures provide a reliable and durable switching function. They combine the tactile feel of a bulky mechanical switch with the compactness of a conventional flexible membrane switch. The benefits of magnetically coupled pushbutton switches have been demonstrated in U.S. Pat. Nos. 5,523,730, 5,990,772 and 6,262,646, incorporated herein by reference. While switches with magnetically coupled armatures already have many applications, it is advantageous to expand the applications of such switches even further, and the present invention relates to an electrical conductor arrangement for use with a magnetically coupled pushbutton switch, the electrical conductor arrangement being particularly useful for medical equipment and other precision devices that require more from a switch than a casual user would demand. A frustration with pushbutton switches that most people have experienced with a calculator or phone is a condition called xe2x80x9ctease.xe2x80x9d Tease is where a user presses on the pushbutton switch and believes a single actuation has occurred when, in fact, either no electrical connection was made or multiple connections where made.
Magnetically coupled pushbutton switches normally have a metal armature that is magnetically held by a coupler magnet layer in a rest position, spaced from switch contacts on a non-conductive substrate layer. A user-provided actuation force applied to a crown of the armature causes it to snap free of the coupler magnet layer and close the switch contacts by electrically connecting them. Release of the actuation force allows the coupler magnet layer to attract the armature back to the rest position to reopen the switch. A non-conductive spacer layer is fixed to the substrate layer, with a cavity in the spacer layer exposing the switch contacts. The coupler magnet layer overlies the spacer layer. The armature is magnetically coupled to the bottom of the coupler magnet layer so that the armature is housed within the cavity in the spacer layer. The armature crown protrudes through an aperture in the coupler magnet layer. Typically, a polyester membrane layer with suitable graphics overlies the coupler magnet layer to direct a user of the switch as to location and function of the switch.
A magnetically coupled pushbutton switch is characteristically designed to be a momentary switch that momentarily affects the logic of external electronics connected to the switch. Once an applied actuation force of a user is released from the pushbutton armature of the switch, the armature does not remain in the actuated position, but is returned to its rest position by the magnetic attraction of the coupler magnet layer. In being returned to its initial rest position, there is typically a return of the logic of the external electronics connected to the switch to their initial state. The electrical conductor arrangement of the present invention is capable of detecting, with great precision, the moment that the switch travels from an unactuated or partially actuated position to a fully actuated position. With the conductor arrangement of the present invention, the external electronics connected to the switch receive a signal indicating the switch is in an unactuated position or partially actuated position. In the prior art, the external electronics knew that the switch was in an unactuated position only because the armature was not connecting any electrical conductors of the switch. In both the switch of the present invention and any of the switches in the prior art, there is a set of electrical conductors on the substrate layer that is electrically connected when the switch is fully actuated.
For the switch of the present invention, there are additional electrical conductors that are normally closed in the unactuated position, but opened during the final travel of the armature into the actuated position. By this method of receiving a signal that positively confirms that the switch is in the xe2x80x9coffxe2x80x9d position until the switch is in the xe2x80x9conxe2x80x9d position, there are two ways the external electronics know that the switch of the present invention was actuated, and how many times. After actuation, the external electronics receive two signals: first, that the switch is no longer in the rest position, and second that the switch is in the actuated position. This is accomplished by having additional electrical conductors on the coupler magnet layer and the membrane overlay. Electrical leads connect each circuit layer of the switch to electronics that are external to the switch. Electrical conductors on the circuit layers are arranged within the switch so that the pushbutton armature of the switch is movable into and out of shorting relationship with the electrical conductors to change the circuit logic for a circuit incorporating the switch. As used herein, the term xe2x80x9ctopxe2x80x9d refers to that surface of any part in a cross sectional figure of the drawings that faces the top edge of the page, while xe2x80x9cbottomxe2x80x9d refers to that surface of any part in a cross sectional figure of the drawings that faces the bottom edge of the page.